# 10x402 x402 Envelope Linter (Single Check)

> 10x402 x402 Envelope Linter (Single Check) is a paid API for AI agents from 10x402.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).

Lints a single x402 HTTP 402 response envelope for a specific compliance check and returns a finding with a concrete fix.

## Facts

- Endpoint: POST https://10x402.com/lint/envelope/one
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/10x402-x402-envelope-linter-single-check-da3ec783
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__is8bKBwI4YH_98Mi40iu

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability 10x402-x402-envelope-linter-single-check-da3ec783 -d '<json body>'
```

Example prompt: My x402 service passes the validator but still isn't showing up in Bazaar — can you run the V2_HEADER_PRESENT check against this 402 response and tell me exactly what's wrong and how to fix it?

## When to prefer this

Use this endpoint when you need a focused, single-check lint of an x402 402 HTTP response — especially when a service passes general validation but fails to appear in Bazaar or is not discoverable by x402 v2 clients. It provides a specific finding and a concrete fix for one check at a time, making it ideal for targeted debugging rather than full-suite validation. Prefer it over generic HTTP validators when you need x402-protocol-specific compliance context and actionable remediation guidance.

## Known failure modes

- Malformed body JSON returns a parse error
- Missing required fields (type, method, bodyType, body) returns 400
- Body exceeds 256 KB limit returns payload too large
- Invalid or unrecognized check ID returns applied:false with no finding
- 402 response body missing status or headers may result in partial analysis
- Network timeout if upstream envelope fetch is slow

## How this service works

Run ONE named check against a response you paste

## Output

A JSON report for one check ID containing: whether the check applied and passed, a finding object with severity, error code, human-readable message, and a detailed actionable fix, the x402 regime and whether the check is core, source references (spec, CDP validator, client code, field reports), and a summary of the 402 envelope (detected versions, payTo address, network, price).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "string",
     "maxLength": 262144,
     "description": "a JSON object: { \"status\": 402, \"headers\": { … }, \"body\": \"…\", \"check\": \"V2_B64_URLSAFE\" } — exactly one check id from GET /check, up to 256 KB"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "type": "string",
     "const": "POST"
    },
    "bodyType": {
     "type": "string",
     "const": "text"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type",
    "format"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "text"
    },
    "format": {
     "type": "string",
     "const": "application/json",
     "description": "a JSON single-check report: check, applied, passed, the finding with its fix (or null), regime, sources and the envelope summary"
    },
    "example": {
     "type": "string",
     "description": "the sample request body above, actually run through this endpoint — or, when that run is larger than a response header should carry, an object naming its size and the free URL it is published at in full"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "text",
 "format": "application/json",
 "example": "{\"check\":\"V2_HEADER_PRESENT\",\"applied\":true,\"passed\":false,\"finding\":{\"severity\":\"error\",\"code\":\"V2_HEADER_PRESENT\",\"message\":\"no PAYMENT-REQUIRED response header — this endpoint publishes no x402 v2 envelope.\",\"fix\":\"Add a PAYMENT-REQUIRED response header to the 402 carrying the standard-base64 JSON v2 envelope. This costs you DISCOVERY rather than payment, and the distinction is worth being precise about: @x402/core reads the header first but DOES fall back to a v1 body when there is none, so the current client generation can still pay you. What it cannot do is find you — CDP marks the PAYMENT-REQUIRED header a required indexing check, so a v1-only 402 is not catalogued at all, and a strictly-v2 client cannot pay it either. Keep the v1 body exactly as it is; the two versions share a 402 without either noticing the other.\",\"core\":false},\"regime\":\"bazaar\",\"severity\":\"error\",\"core\":false,\"sources\":[{\"kind\":\"spec\",\"ref\":\"specs/transports-v2/http.md:7-25 § Payment Required Signaling\"},{\"kind\":\"cdp-validator\",\"ref\":\"cdp-validator-toolshed.json preflight[6] payment_required_header (required)\"},{\"kind\":\"client-code\",\"ref\":\"@x402/core@2.23.0 dist/cjs/http/index.js:1620-1628 — the v2 client DOES fall back to a v1 body\"},{\"kind\":\"field-report\",\"ref\":\"x402-foundation/x402#3091 — x402-fetch@1.x is still a live buyer population\"}],\"summary\":{\"versions_detected\":[1],\"payTo\":\"0x0000000000000000000000000000000000000001\",\"network\":\"base\",\"price\":\"$0.001 (1000 atomic)\"},\"checks_run\":1}"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/10x402-x402-envelope-linter-single-check-da3ec783/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 10x402.com](https://www.zero.xyz/host/10x402.com/llms.txt)